During the exploration of oil and gas, measuring the resistivity and permittivity of a formation downhole can provide important data for geologist and petro physicist to evaluate formation property, such as whether a formation contains water or hydrocarbons. Due to deposition, fractures, and the lamination of layers within a formation, etc., formations downhole will typically exhibit some form of anisotropy. The resistivity and permittivity anisotropy of a formation downhole can represent this formation anisotropy. The anisotropy has large effects on the resistivity and permittivity measurements, which will affect the accuracy of formation evaluation.
Anisotropy is commonly modeled using transverse isotropy (TI). A formation will exhibit TI-anisotropy when it has an axis of symmetry such that along any direction parallel (or transverse) to this axis the material properties of the formation are the same. However, between the axis of symmetry and a direction perpendicular to the axis of symmetry, one will see a material property difference.
Electromagnetic tools used in wireline and measurement while drilling (MWD) applications are typically used for measuring formation resistivity and dielectric permittivity. However, some electromagnetic tools, such as resistivity and permittivity measurement tools, used in wireline haven't used in MWD.
Also, although these electromagnetic tools used in MWD are capable of taking measurements while drilling, these tools are currently focused on measuring TI-anisotropy of a formation in one direction relative to the axis of the tool, and cannot measure the anisotropy of a formation in multiple directions simultaneously.
Further, another limitation of many electromagnetic tools which can operate in water base-mud is that they cannot operate in oil based mud due to the non-conductive nature of some oil based mud. Therefore, having the ability to operate in both oil based mud and water base mud environment is one advantage some electromagnetic tools have over others. By operating electrical electromagnetic tools using higher frequencies (in the range of hundreds of Megahertz to Gigahertz), these tools are better able to take measurements in oil based mud as well as in water base mud.
It is therefore desirable to have an apparatus and method for taking quantitative measurements of formation parameters, such as resistivity and permittivity, in multiple directions simultaneously. Moreover, it is also desirable to be able to take quantitative measurements of the formation parameters in both water based and oil based mud. The subject matter of the present disclosure is directed to overcoming, or at least reducing the effects of, one or more of the problems set forth above.